1. Field of the Invention
This invention relates to power operated sabre saws and, more particularly, to a novel and improved crosshead forming part of a scotch yoke mechanism for reciprocating the saw bar thereof.
2. Description of the Prior Art
Sabre saws, and especially general purpose electrically driven sabre saws for use by craftsmen and handymen have become popular and versatile tools for cutting wood, light sheet metal, plastic, composition board, and the like. Such saws are known comprising a generally cylindrical housing containing a built-in electric motor which drives a reduction gear train to rotate an eccentric crank pin which in turn is operatively associated with a crosshead mounted for movement with an elongated saw bar in turn journalled for reciprocatory movement generally perpendicular to the motor axis. Because the reciprocation of the saw bar and crosshead provides a rapidly varying load to the motor and substantial vibration, various schemes have been devised in attempts to reduce the vibration and load variation associated with the reciprocation of the saw bar.
In order to resist the shock and inertial forces imposed upon the crosshead from the rapid changes in direction, the crosshead needs to be relatively strong, rigid and tough. Generally, this has been achieved by machining the crosshead from solid metal stock, which is a relatively expensive process and results in a crosshead of relatively large mass, exacerbating the vibration and shock loading accompanying the reversals of movement of the saw bar. It has been generally believed that a saw bar crosshead could not successfully be formed from sheet stock, by bending, having sufficient rigidity, toughness and strength to withstand for an economically worthwhile period of time the shock, stress and vibration.